How can I increase the log level of winbind or samba without restarting the services?

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux 8+
  • Red Hat Enterprise Linux 6 and 7 (Refer Diagnostic Steps for workaround)
  • Samba >= 3

Issue

  • I don't want to restart winbind or samba to increase the log levels.
  • I need increased logging while a problem is occurring but increasing the log level through the smb.conf requires a restart of the services which can temporarily fix an issue and requires me to wait for another occurrence to get the logs I need.
  • Continuous level 10 logging can cause a performance hit and fill up disk space.

Resolution

smbcontrol can send messages to control smbd, nmbd or winbind process

Note: RHEL 7 hosts are affected by Bug This content is not included.205004 - smbcontrol winbindd debug is not possible,
which prevent change log level of running process. Refer Diagnostic Steps for workaround.

1. Query current debug level (optional)

To query the current log level of smb, winbind, and nmbd

# smbcontrol smbd debuglevel
# smbcontrol winbind debuglevel
# smbcontrol nmbd debuglevel

The output for smbcontrol smbd debuglevel looks like:

PID 56898: all:10 tdb:10 printdrivers:10 lanman:10 smb:10 rpc_parse:10 rpc_srv:10 rpc_cli:10 passdb:10 sam:10 auth:10 winbind:10 vfs:10 idmap:10 quota:10 acls:10 locking:10 msdfs:10 dmapi:10 registry:10 scavenger:10 dns:10 ldb:10 tevent:10 auth_audit:10 auth_json_audit:10 kerberos:10 drs_repl:10 smb2:10 smb2_credits:10 dsdb_audit:10 dsdb_json_audit:10 dsdb_password_audit:10 dsdb_password_json_audit:10 dsdb_transaction_audit:10 dsdb_transaction_json_audit:10 dsdb_group_audit:10 dsdb_group_json_audit:10

2. Set the debug level

To set the log level of smb, winbind, and nmbd

# smbcontrol smbd debug     10
# smbcontrol winbind debug  10
# smbcontrol nmbd debug     10

A. Advanced Usages

You can also set the log level for a specific samba process, like:

# smbcontrol <pid> debug 10

or query the current level:

# smbcontrol <pid> debuglevel

Root Cause

Increasing the logs while a problem is occurring can help reduce the impact of high log levels over an extended period such as disk usage and system performance. Setting the logs without restarting the daemon is also useful for cases when restarting the service temporarily fixes the problem for a period of time. The drawback is that increasing logs after a problem has occurred may result in missing information but this isn't needed in cases when a reproducer is known.

Diagnostic Steps

If high level log items still not there, it is possible you are affected by Bug This content is not included.205004 - smbcontrol winbindd debug is not possible.

RHEL 8 and later already fixed. RHEL 7 and earlier are still affected.

Workaround

You will need to stop and start Samba services (e.g. smb, winbind) once. After that, you can change log level on the fly.

1. Stop all running Samba services (winbind, smb, nmb)
# service winbind stop; service smb stop

If you also have nmb running:

# service nmb stop
2. Increase log level to maximum

Edit /etc/samba/smb.conf and set the following variables in the [global] section of the config:

log level = 10
debug pid = true
max log size = 0
3. Start the samba services
service winbind start; service smb start

If you also need NetBIOS over IP, start nmb with:

service nmb start

Now you can change the log level on-the-fly without restart samba services.

4. Lower the log level on-the-fly (optional)

If you don't need verbose level now, you can lower it to 0 like:

smbcontrol smbd debug     0
smbcontrol winbind debug  0

If you also have nmb running:

smbcontrol nmbd debug  0
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